The laser peening (“LP”) process, a substitute process for traditional shot peening, is a coldworking process used to produce a compressive residual stress layer and modify mechanical properties of materials by impacting the material with enough force to create plastic deformation. The residual stresses created by the LP process increase a material's resistance to fatigue and stress, and the LP process can be used to strengthen and harden materials. LP uses high energy laser pulses to lase both transparent and opaque overlays on a surface of a workpiece to generate a plasma plume and cause a rapid rise of pressure on the surface of a workpiece. This pressure creates and sustains a shockwave, which propagates through a workpiece material. The shockwave generated by LP induces coldwork into the microstructure of the workpiece material and contributes to the increased performance of the workpiece material. As the shockwave travels into the workpiece, some of the energy of the wave is absorbed during the plastic deformation of the workpiece material. This is also known as coldworking. The shockwave permanently stretches the internal structure of the workpiece material. This plastic deformation generates compressive residual stresses in the workpiece material, and increases the strength of the workpiece material. LP uses a laser pulse width of about 8 nanoseconds (ns) to about 40 ns. A typical spot diameter for a laser beam in LP is about 1.0 mm to about 6.0 mm. Fluence is the measure of energy delivered per unit area, and in LP applications, fluence is typically over 100 J/cm2.
Current LP equipment is large, and a workpiece must either be positioned to align with LP equipment or LP equipment must be manually positioned around a workpiece for LP processing. While manual positioning of a workpiece and LP equipment is acceptable for relatively small workpieces, use of such LP techniques is more challenging with larger assemblies such as turbine blades, engine components, and the like. U.S. Pat. Nos. 5,741,559; 6,288,358; 6,528,763; and 6,867,390 (all to LSP Technologies, Inc.), all of which are incorporated herein by reference in their entireties, disclose improvements to laser peening system mobility.
The present application is directed to novel systems and methods for automating a LP process.